obama's second inauguration comes four years after he became the first black president and just over 16 years since he was first sworn into office as an illinois state legislator. inauguration day began with a prayer service at st. john's episcopal church across the street from the white house. later, it was on to the capitol building for the swearing-in. a planning official said the turnout on the mall was more than 800,000 people fewer than the record crowd that watched the first inauguration in 2009. first supreme court justice sonia sotomayor swore in joe biden. then chief justice roberts administered the oath to president obama. >> preserve, protect, and defend -- >> preserve, protect, and defend -- >> the constitution of the united states -- >> the constitution of the united states. >> so help you god? >> so help me god. >> congratulations, mr. president. [ cheers ] >> reporter: president obama's left hand was on two bibles, one belonging to abraham lincoln, the other to martin luther king jr. following his inaugural address and a signing ceremony in the capitol, the president